Design_Optimization_of_a_wishbone_suspension_of_a_car_ganzi_suresh_1

DESIGN OPTIMIZATION OF A WISHBONE

SUSPENSION OF A PASSENGER CAR

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY COLLEGE OF ENGINEERING (AUTONOMOUS) ANANTHAPURAM.

Ganzi Suresh

Aim of this project is to optimize the thickness of the upper control arm of wishbone

suspension system to loading. The present project work has created a Finite Element Model

for wishbone suspension using HYPERMESH V11. Pre- Processing steps such as updating of

element type, material properties, application of loads and boundary conditions. The element

type considered for the analysis is second order R- Trais, meshing type is tetra mesh.

M.Tech, Product Design | Jawaharlal Nehru Technological University Ananthapuram, 2011-13.

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DESIGN OPTIMIZATION OF A WISHBONE SUSPENSION

OF A PASSENGER CAR

A Thesis

Submitted in partial fulfillment of the Requirements for the award of the Degree in

Master of Technology

In

Mechanical Engineering

(Product Design)

By

GANZI SURESh

Roll No: 11001D3407

Under the esteemed guidance of

Dr. B. Durga Prasad M.Tech., Ph.D.

Prof. Dept. of Mechanical Engineering,

J.N.T.U.A College of Engineering (Autonomous).

DEPARTMENT OF MECHANICAL ENGINEERING

JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY

COLLEGE OF ENGINEERING (AUTONOMOUS) ANANTHAPURAM.

ANANTHAPURAM – 515 002

ANDHRA PRADESH

2013


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ACKNOWLEDGEMENT

I would like to thank Dr. B. DurgaPrasad M.Tech., P.h.D. Professor Mechanical Engineering

Dept, JNTUCEA, Ananthapuram,, for advising this work and for allowing me the freedom to

pursue this optimization project. His advice and leadership was plentiful and much

appreciated.

I would also like to acknowledge Dr. M. YOHAN M.Tech., Ph.D. Professor & Head of

Mechanical Engineering Dept, JNTUCEA, Ananthapuram, who has been inspiring and

encouraging throughout the project.

I wish to place on record my sincere thanks to Dr.K.S.R.ANJANEYULU, Principal

JNTUCEA, Ananthapuram.

I express my gratitude to Mr.P.Hithayathullah technical manager, Mr. E. Venkatesh,

Mr. Amith Singh and Mr. S. Muhassin of Fexilon Technologies Bangalore, for their timely

support in providing me all necessary help for the smooth progress and completion of this

project.

I am very much grateful to my parents GANZI VENKATA LAKSHMI and GANZI

RAMAMOHAN for their cooperation in completing this project.

I am also very thankful to the entire Faculty and Non-Teaching staff of Mechanical

Engineering Dept, for their support and cooperation.

I regret, if any acknowledgement that is due has been missed out or found inadequate.

With Regards,

Ganzi Suresh.


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ABSTRACT

The suspension of a road vehicle is usually designed with two objectives namely: to isolate

the vehicle body from road irregularities and to maintain contact of the wheels with the

roadway. Independent suspension systems can be provided by a variety of linkages between

the stub axle carrying the wheel and the vehicle chassis. Most popular combinations in

modern passenger cars are the double wishbone suspension systems.

The double wishbone configurations can give vertical movement close to perpendicular

relative to the tier-contact surface. The wishbone linkages arrangement provides very good

wheel adhesion and optimum wheel control. In addition, the double wishbone suspension

system provides a whole new range of possibilities in regard to the application of computer

systems which would provide active suspension control to suit various conditions.

The main aim of this project is to optimize the thickness of the upper control arm of

wishbone suspension system to loading. The present project work has created a Finite

Element Model for wishbone suspension using HYPERMESH V11. Pre- Processing steps

such as updating of element type, material properties, application of loads and boundary

conditions. The element type considered for the analysis is second order R- Trais, meshing

type is tetra mesh.

Processing is done internally mathematical equations by the software. The results in the form

of stress deformation are shown by contour plots. The factor of safety for the upper control

arm calculated, based on von-Misses theory of failure is found to be 5.64. Desired factor of

safety for the suspension components in 3.49. Therefore there is need to optimize the upper

control arm.

Optimization of the thickness of upper control arm of wishbone suspension system is done in

terms of reduction in its weight and there by the fixed cost, operation cost are decreased

drastically. Thickness of the control arm is varied in different steps to optimize it, so as a

factor of safety of 3.5 is obtained. It is found to be 10mm thickness for upper control arm

satisfies the strength criteria and the factor of safety is within the limits.


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CONTENTS

ABSTRACT 4

CONTENTS 5

LIST OF FIGURES 8

LIST OF TABLES 11

NOMENCLATURE 12

CHAPTER: 1 INTRODUCTION:

1.1 Suspension system 13

1.2 The need for suspension 15

1.3 Types of suspension systems 16

1.4 Need for optimization of design of suspension systems 20

1.5 Thesis outline 20

CHAPTER: 2 LITERATURE REVIEW

2.1 Double Wishbone Suspension System 22

2.2 History of optimization 25

2.3 Factor of safety 26

2.4 Problem definition 27

CHAPTER: 3 FINITE ELEMENT METHOD / ANALYSIS (FEM /A)

3.1 Definition of FEM 28

3.2 Methods in FEM 28

3.3 Absolute vs Relative design 29

3.4 Theoretical Finite Element Analysis 30

3.5 Software based FEM 30

3.6 Types of analysis 32

3.7 Optimization 34

3.8 Engineering applications of optimization 34


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CHAPTER: 4 SOFTWARE REVIEW

4.1 Hypermesh V 11 35

4.2 Radioss 36

4.3 Hyperview 36

CHAPTER: 5 PRE – PROCESSING

5.1 Initial geometry 38

5.2 Material properties 39

5.3 Mesh generation 40

5.4 Boundary conditions and loading 46

CHAPTER: 6 PROCESSING

6.1 Set up for design space 49

6.2 Load calculation 50

CHAPTER: 7 ANALYSIS

7.1 Linear Static Analysis 53

7.2 Buckling Analysis 58

7.3 Modal Analysis 62

CHAPTER: 8 POST-PROCESSING

8.1 Comparison of results - Linear Static Analysis 66

8.2 Comparison of results - Buckling Analysis 66

8.3 Comparison of results - Modal Analysis 67

8.4 Upper control arm Thickness vs Volume 67

8.5 Calculation of Factor of Safety 68

8.6 Economic considerations 68

8.7 Advantages of optimized model 69


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CHAPTER: 9 SUMMARY AND CONCLUSION

9.1 Summary of existing control arm 70

9.2 Summary of proposed control arm 70

9.3 Conclusion 71

9.4 Future scope of work 71

REFERENCE 72


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LIST OF FIGURES

Figure : 1.1 Solid Axle 17

Figure : 1.2 Dead Axle 18

Figure : 1.3 Macpherson Strut 19

Figure : 1.4 Double Wishbone 20

Figure : 2.1 Wishbone 22

Figure : 2.2 Camber angle 23

Figure : 2.3 Positive and Negative camber angle 23

Figure: 2.4 Maxima and Minima 25

Figure : 3.1 a & b Buckling analysis 33

Figure : 5.1 Geometry of a double wishbone 38

Figure : 5.2 Wishbone setup 39

Figure : 5.3 1D Meshing 40

Figure : 5.4 3D / Solid Meshing 41

Figure : 5.5 Wheel hub 42

Figure : 5.6 Suspension spring 42

Figure : 5.7 Rear Suspension 43

Figure : 5.8 Upper control arm 43

Figure : 5.9 Lower control arm 44

Figure : 5.10 Assembly of double wishbone 44

Figure : 5.11 Straight beams 45

Figure : 5.12 Wagon wheel beams 46

Figure : 5.13 Constraints Six Dofs at rear suspension 47

Figure : 5.14 Constraints 1 & 3 Dofs on the spring 47

Figure : 5.15 Loading 48

Figure : 6.1 Set up for design space 49


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Figure : 6.2 Assembly of Modified control arm 50

Figure : 6.3 Force at node 1045060 52

Figure : 6.4 Force at node 1045061 52

Figure : 7.1 Stress – Strain Curve for Linear Static 53

Figure : 7.2 Force vs Time 54

Figure : 7.3 Displacement at 15mm Thickness 54

Figure : 7.4 Von-Misses at15mm Thickness 55

Figure : 7.5 P1 Major (Tension) at 15mm Thickness 55

Figure : 7.6 P3 Minor (Compression) at 15mm Thickness 56

Figure : 7.7 Displacement at 10mm Thickness 56

Figure : 7.8 Von–Misses at 10mm Thickness 57

Figure : 7.9 P1 Major (Tension) at 10mm Thickness 57

Figure : 7.10 P3 Minor (Compression) at 10mm Thickness 57

Figure : 7.11 Buckling Analysis before Optimization

15mm Thickness Mode1 58

Figure : 7.12 Mode 2 59




Figure : 7.16 Buckling Analysis after Optimization

10mm Thickness Mode 1 60






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Figure : 7.21 Modal analysis before optimization

15 mm thickness mode 1 62





Figure : 7.26 Modal analysis after optimization

10 mm thickness mode 1 64






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LIST OF TABLES

Table : 3.1 Methods to solve engineering problem 29

Table : 5.1 Material properties 39

Table : 5.2 Criteria for meshing 41

Table : 8.1 Linear Static analysis 66

Table : 8.2 Buckling analysis 66

Table : 8.3 Modal analysis 67

Table : 8.4 Thickness vs Volume 67

Table : 9.1 Summary of existing control arm 70

Table : 9.2 Summary of proposed control arm 70


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NOMENCLATURE

X, Y, Z = Three linear axes

U, V, W = Three rotational axes

FX, FY, FZ = Force In x, y, z axis respectively

MX, MY, Mz = Moment in x, y, z axis respectively

SIMO = Single Input Multiple Outputs

MISO = Multiple Inputs Single Output

MIMO = Multiple Inputs Multiple Outputs

AISC = Automotive Industry Standards Committee

HTML = Hyper Text Machine Language

SLA = Short Long Arms

FOS = Factor of Safety

UTS = Ultimate Tensile Stress

FEM = Finite Element Method

FEA = Finite Element Analysis

NVH = Nose Vibration and Harshness

FVM = Finite Volume Method

CAE = Computer Aided Engineering

CAD = Computer Aided Design

CAM = Computer Aided Manufacturing

CFD = Computational Fluid Dynamics

Kg = Kilogram

Mm = Millimeter

M pa = Mega Pascal

SF = Safety Factor


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FE = Finite Element

[K] = Global stiffness matrix

[F] = Nodal force vector

[µ] = Nodal displacement vector

σ = Stress

ɛ = Strain

ρ = Density

µ = Poisson’s ratio

∑ = Summation

R – Trai’s = Right angle triangles

D = Dimension

Π = Pie

r = Radius

N = Newton

E = Elastic Modulus


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CHAPTER 1

INTRODUCTION

1.1 SUSPENSION SYSTEM :

Suspension is the term given to the system of springs, shock absorbers and linkages that

connects a vehicle to its wheels and allows relative motion between the two. Suspension

systems serve a dual purpose contributing to the vehicle's road holding/handling and braking

for good active safety and driving pleasure, and keeping vehicle occupants comfortable and

reasonably well isolated from road noise, bumps, and vibrations, etc. These goals are

generally at odds, so the turning of suspensions involves finding the right compromise. It is

important for the suspension to keep the road wheel in contact with the road surface as much

as possible, because all the road or ground forces acting on the vehicle do so through the

contact patches of the tires. The suspension also protects the vehicle itself and any cargo or

luggage from damage and wear. The design of front and rear suspension of a car may be

different.

1.1.1 History

Leaf springs have been around since the early Egyptians. Ancient military engineers used leaf

springs in the form of bows to power their siege engines, with little success at first. The use

of leaf springs in catapults was later refined and made to work years later. Springs were not

only made of metal, a sturdy tree branch could be used as a spring, such as with a bow.

1.1.2 Horse drawn vehicles

By the early 19th

century, most British horse carriages were equipped with springs; wooden

springs in the case of light one-horse vehicles to avoid taxation, and steel springs in larger

vehicles. These were made of low-carbon steel and usually took the form of multiple layer

leaf springs.

The British steel springs were not well suited for use on America's rough roads of the time,

and could even cause coaches to collapse if cornered too fast. In the 1820s, the Abbot

Downing Company of Concord, New Hampshire re-discovered the antique system whereby

the bodies of stagecoaches were supported on leather straps called "thorough braces", which

gave a swinging motion instead of the jolting up and down of a spring suspension (the

stagecoach itself was sometimes called a "thorough brace").

1.1.3 Automobiles

Automobiles were initially developed as self-propelled versions of horse drawn vehicles.

However, horse drawn vehicles had been designed for relatively slow speeds and their

suspension was not well suited to the higher speeds permitted by the internal combustion

engine. In 1901 Mors of Paris first fitted an automobile with shock absorbers. With the

advantage of a dampened suspension system on his 'Mors Machine', Henri Fournier won the

prestigious Paris-to-Berlin race on the 20th of June 1901. Fournier's superior time was 11 hrs

46 min 10 sec, while the best competitor was Leonce Girardot in a Panhard with a time of 12

hrs 15 min 40 sec. In 1920, Leyland Motors used torsion bars in a suspension system. In1922,

http://en.wikipedia.org/wiki/Spring_%28device%29

http://en.wikipedia.org/wiki/Shock_absorber

http://en.wikipedia.org/wiki/Linkage_%28mechanical%29

http://en.wikipedia.org/wiki/Vehicle

http://en.wikipedia.org/wiki/Wheel

http://en.wikipedia.org/wiki/Automobile_handling

http://en.wikipedia.org/wiki/Brake

http://en.wikipedia.org/wiki/Rear_suspension

http://en.wikipedia.org/wiki/Leaf_springs

http://en.wikipedia.org/wiki/Leaf_springs

http://en.wikipedia.org/wiki/Concord,_New_Hampshire

http://en.wikipedia.org/wiki/Stagecoach

http://en.wikipedia.org/wiki/Mors_%28automobile%29

http://en.wikipedia.org/wiki/Paris


http://en.wikipedia.org/wiki/Leyland_Motors_Ltd

http://en.wikipedia.org/wiki/Torsion_bar_suspension


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independent from suspension was pioneered on the Lancia Lambda and became more

common in mass market cars from 1932.

1.2 THE NEED FOR SUSPENSION:

The purpose of the complete suspension system is to isolate the vehicle body from road

shocks and vibrations which would otherwise be transferred to the passengers and load. It

must also keep the tires in contact with the road, regardless of road surface. A basic

suspension system consists of springs, axles, shock absorbers, arms, rods, and ball joints. The

spring is the flexible component of the suspension. Basic types are leaf springs, coil springs,

and torsion bars. Modern passenger vehicles usually use light coil springs. Light commercial

vehicles have heavier springs than passenger vehicles, and can have coil springs at the front

and leaf springs at the rear.

The study of the forces at work on a moving car is called vehicle dynamics. Some of the

concepts are needed to be understood in order to appreciate why a suspension is necessary in

the first place. Most automobile engineers consider the dynamics of a moving car from these

perspectives:

1.2.1 Ride – A car's ability to smooth out a bumpy road.

1.2.2 Handling – A car's ability to safely accelerate, brake and corner.

These two characteristics can be further described in three important principles - Road

Isolation, Road Holding and Cornering. These principles are explained below and also how

engineers attempt to solve the challenges unique to each.

1.2.3 Road Isolation – The vehicle's ability to absorb or isolate road shock from the

passenger compartment. Allow the vehicle body to ride undisturbed while traveling over

rough roads. Absorb energy from road bumps and dissipate it without causing undue

oscillation in the vehicle.

1.2.4 Road Holding – The degree to which a car maintains contact with the road surface in

various types of directional changes and in a straight line (Example: The weight of a car will

shift from the rear tires to the front tires during braking. Because the nose of the car dips

toward the road, this type of motion is known as "dive". The opposite effect "squat" occurs

during acceleration, which shifts the weight of the car from the front tires to the back.

Minimize the transfer of vehicle weight from side to side and front to back, as this transfer of

weight reduces the tire's grip on the road.

1.2.5 Cornering – It is the ability of a vehicle to travel a curved path. Minimize body roll,

which occurs as centrifugal force pushes outward on a car's center of gravity while cornering,

raising one side of the vehicle and lowering the opposite side. Transfer the weight of the car

during cornering from the high side of the vehicle to the low side.

http://en.wikipedia.org/wiki/Lancia_Lambda


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1.3 TYPES OF SUSPENSION SYSTEMS:

The two main types of suspension systems found in cars are dependent and independent.

These suspension systems also apply to other vehicles such as semi trucks. Each type of

suspension system utilizes springs and shock absorbers. There are various types of springs

including coil springs, torsion bars and leaf springs. If a vehicle only had springs it would

boat and wallow along with the road making the ride very uncomfortable. Imagine the

suspension just mimicking what it is encountering on the road rather than absorbing it. This is

where shock absorbers come in which are technically dampers. They absorb any larger than

average bumps in the road, so minimal motion is transmitted to the chassis. In addition, shock

absorbers keep the suspension at its maximum travel by pushing it towards the road, which

also helps keeps your tires on the road. Many modern cars have a coil-over-oil unit which

incorporates both a shock absorber and spring into one product.

1.3.1 Dependent Suspension System

Dependent suspension systems get their name because each of the front or rear wheels is

dependent on the wheel opposite of it. This type of suspension system is only found on

modern trucks and off road vehicles but a number of years ago it was common on cars as

well. The major downside to a dependent suspension system is that the wheels are linked, if

one wheel is set into oscillation and the other is not, it sets up a gyroscopic torque around the

steering axis. This force will start to turn the axle left to right and due to the axles inertia, it

will amplify the force of the original oscillation. To put that simpler, if the tire on the right

side hits a bump it will directly affect the left side and can even cause a larger effect than the

original bump. Another downfall of a dependent suspension system is that it weighs more

than an independent system. This is because there are a number of parts that are needed on a

dependent system that are not needed on an independent system.

1.3.1.1 Solid Axle :

A beam axle is a suspension system, also called a solid axle, in which one set of wheels is

connected laterally by a single beam or shaft. A live axle is a type of beam axle in which the

shaft (or shafts, since live axles, while connected to move as a single unit, are seldom one

piece) also transmits power to the wheels; a beam axle that does not also transmit power is

sometimes called a dead axle. Beam axles are commonly used at the rear wheels of a vehicle,

but historically they have also been used as front axles in rear-wheel-drive cars. Ford used

beam axles across the range until 1949, only being phased out in Europe as recently as the

early 1960s with the Ford Popular being suspended.

Beam axles are typically suspended either by leaf springs or coil springs. In some cases, a

Pan hard rod or similar device may be used to control the lateral motion of the axle. A similar

suspension is the Twist-beam rear suspension, in which the beam axle also functions as an

anti-roll bar to control the roll motion of the body. The principal advantage of the beam axle

is that it is simple and cheap to manufacture. It also engages little or no interior volume

within the vehicle. Its drawbacks are that it does not allow each wheel to move independently

in response to bumps, and the mass of the beam is part of the unsprung weight of the vehicle,

which can further reduce ride quality

http://camptwo.com/question/31/how-many-different-kinds-of-suspension-systems-can-be-used-in-cars


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Figure : 1.1 Solid axle

A beam axle is a suspension system, also called a solid axle, in which one set of wheels is

connected laterally by a single beam or shaft

Because beam axles do not ever exhibit any camber change as the suspension travels, they are

ideal for carrying heavy or varying loads. Although this negatively impacts cornering

compared to other suspension designs (because the wheels have zero camber gain during

body roll), beam axles are nearly universally used in heavy-duty trucks. One notable

exception is the Czech manufacturer Tatra, who instead use swing-axles in conjunction with a

central 'backbone' chassis. Most light and medium duty pickup trucks and vans also use a

beam axle, at least in the rear. Beam axles have an important advantage for off-road

applications, as they provide better vehicle articulation and durability in a high load

environment.

1.3.1.2 Dead Axle :

On front-wheel-drive vehicles, a simple beam axle can be used on the rear, with coil spring

suspension and control arms for location. This is called a dead axle, since it only supports the

vehicle and doesn’t transmit any drive. It is also non-independent, as deflection of a wheel on

one side of the vehicle will be transferred to the other wheel. On some vehicles, this is

reduced by using a U-shaped axle beam, with a torsion bar mounted inside it. Trailing arms

are welded to the beam, to locate the axle longitudinally. A lateral rod prevents lateral

movement when cornering, and coil springs provide for suspension. The torsion bar is

connected between the left and right wheel units, and deflection of the wheel on one side

causes the axle and its torsion bar to twist together. Passenger cars no longer use beam axle

front suspension, but it is still common on heavy commercial vehicles, and some 4-wheel-

drives.Trucks use an I-beam, in most cases located by leaf springs.

Coil springs may also be used for front and rear, and as with other beam axle designs, control

arms and a lateral rod must be used for location.


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Figure : 1.2 Dead axle

1.3.2 Independent Suspension System:

An independent suspension system gets its name because the wheels on either side of the car

are independent from one another. The only exception to this is an anti-roll bar that connects

the two wheels, to prevent the cars suspension from rolling as it corners. There are a number

of independent suspension types such as, coil spring type 1, coil spring type 2, multi-link,

trailing-arm, twin I-beam, moulton rubber and transverse leaf spring. The major difference

between independent suspension and dependent suspension is that when a car with

independent suspension hits a bump it only affects the wheel that hit the bump. This offers

many advantages such as, better ride comfort, better traction, more stability and an overall

safer vehicle.

- Macpherson Struts suspension system

- Double Wishbone Suspension System

1.3.2.1 Macpherson Struts

A MacPherson strut is a type of shock absorber that has a more structural role in a vehicle’s

suspension. Named after its creator, “MacPherson strut” refers both to the component and

the suspension design that employs it. The strut includes a shock absorber element but also

plays a role in positioning the wheels. Struts are used for the front or rear axle or both and are

the most common suspension type in passenger cars today. Each strut runs directly through a

coil spring and resides in a tall channel called a tower, the top of which may be visible under

the hood near the back of the engine compartment. This “coil-over” design is space efficient,

as is the strut’s elimination of the space-robbing upper control arm used in earlier suspension

designs. The low overall parts count reduces the unspring weight, for a smoother ride. Struts

are also used in a modified MacPherson design that locates the springs inboard, rather than

around the struts an approach that’s claimed to reduce vibration in the steering wheel.


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Figure : 1.3 MacPherson strut

1.3.2.2 Double Wishbone

The double wishbone suspension is a very popular type of suspension foundon mid-range to

high-end cars. It is an independent suspension design using two (occasionally parallel)

wishbone-shaped arms to locate the wheel as shown in Fig. 1.4. Each wishbone or arm has

two mounting points connected to the chassis and one joint at the knuckle to accept the

steering input. The shock absorber and coil spring are mounted on the wishbones to control

its vertical movement. Double wishbone designs allow the engineer to carefully control the

motion of the wheel throughout the suspension travel, controlling parameters such as camber

angle, caster angle, toe, roll centre height, scrub radius, scuff and more thereby resulting in a

better tuned suspension system for good ride, handling etc. These parameters affect factors

from lateral force to steering effort to anti-dive/ant-squat characteristics of the vehicle. Two

of the wheel parameters that significantly affect the car handling characteristics are camber

and toe.


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Figure : 1.4 Schematic view of Double wishbone suspension

1.4 NEED FOR OPTIMIZATION OF DESIGN OF SUSPENSION

SYSTEMS:

Automobiles commuting everyday will experience lot of ground vibrations which is

transmitted to the suspension system through the tires of the wheel hub. The mechanism is

subjected to varying loads at a given instant of time. Due to the continuous loading on the

components of a suspension system, the parts are subjected to failure. Due to the sudden

bumps on the roads the components may fail well below its working strength. So there is a

need to assess the working strength of a component.

1.5 THESIS OUTLINE :

Chapter 1 deals with the introduction in to the suspension system, its types, need for

suspension and briefly discussed about the need for optimization of suspension system.

Chapter 2 discusses about the literature survey carried out in order to understand the

suspension system, mechanism and concept of optimization. It also gives brief introduction of

Factor of Safety.

Chapter 3 deals with Finite Element Analysis like methods followed in FEM. It discusses

both theoretical and software based FEM. It gives description about the types of analysis

followed in industries and engineering application of optimization.

Chapter 4 constitute the software review as Hypermesh v11, Radioss and Optistruct.

Chapter 5 deals with pre-processing as initial geometry, material properties, generation of

mesh for the component and applying the boundary conditions.

Chapter 6 constitute processing as setup for the design space and load calculations.

Chapter 7 discusses about the Analysis like linear static analysis, buckling analysis and

modal analysis.


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Chapter 8 deals with the post processing i.e viewing the results. It also discusses the

economic consideration and advantages of optimized modal.

Chapter 9 gives a result summary, conclusion and scope for the future work that can be

carried out.


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CHAPTER 2

LITERATURE REVIEW

2.1 DOUBLE WISHBONE SUSPENSION SYSTEM:

In automobiles, a double wishbone (or upper and lower A-arm) suspension is an independent

suspension design using two (occasionally parallel) wishbone-shaped arms to locate the

wheel. Each wishbone or arm has two mounting points to the chassis and one joint at the

knuckle. The shock absorber and coil spring mount to the wishbones to control vertical

movement. Double wishbone designs allow the engineer to carefully control the motion of

the wheel throughout suspension travel, controlling such parameters as camber angle, caster

angle, toe pattern, roll center height, scrub radius, scuff and more.

2.1.1 Implementation

Figure : 2.1 Wishbones and upright painted yellow

The double-wishbone suspension can also be referred to as "double A-arms," though the arms

themselves can be A-shaped, L-shaped, or even a single bar linkage. A single wishbone or A-

arm can also be used in various other suspension types, such as MacPherson strut and

Chapman strut. The upper arm is usually shorter to induce negative camber as the suspension

jounces (rises), and often this arrangement is titled an "SLA" or "short long arms"

suspension.

When the vehicle is in a turn, body roll results in positive camber gain on the lightly loaded

inside wheel, while the heavily loaded outer wheel gains negative camber. Between the

outboard end of the arms is a knuckle with a spindle (the kingpin), hub, or upright which

carries the wheel bearing and wheel. Negative response of the vehicle is affected by camber

angle in three following cases:

http://en.wikipedia.org/wiki/A-arm

http://en.wikipedia.org/wiki/Suspension_%28vehicle%29

http://en.wikipedia.org/wiki/Independent_suspension

http://en.wikipedia.org/wiki/Independent_suspension

http://en.wikipedia.org/wiki/Furcula

http://en.wikipedia.org/wiki/Chassis


http://en.wikipedia.org/wiki/Spring_%28device%29

http://en.wikipedia.org/wiki/Camber_angle

http://en.wikipedia.org/wiki/Caster_angle

http://en.wikipedia.org/wiki/Caster_angle

http://en.wikipedia.org/wiki/Toe_%28automotive%29

http://en.wikipedia.org/wiki/Roll_center

http://en.wikipedia.org/wiki/Scrub_radius



http://en.wikipedia.org/wiki/MacPherson_strut

http://en.wikipedia.org/wiki/Chapman_strut

http://en.wikipedia.org/wiki/Short_long_arms_suspension


http://en.wikipedia.org/wiki/Kingpin_%28automotive_part%29

http://en.wikipedia.org/wiki/Bearing_%28mechanical%29


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Figure : 2.2 Size of the camber angle

In zero camber case, the wheel is perpendicular to the road surface and its steering is

relatively difficult. This case is used in tracks.

Negative camber case for separate suspension systems to increase the level of reliance

vehicle on the road, is used in back wheels, but not in front wheels

Positive camber for front wheels between 0 to 2degrees is selected because:

* In the positive camber, the lateral force is cause to direct wheel upward and thus the force

on the trunnion nut removed and the two cone bearing will be established well(Fig 2.3).

Figure : 2.3 The effects of positive and negative camber angle

When the wheel is lie under the loads, it could be lie in vertical state. Whenever camber angle

is not positive, bending moment take the front wheels to the negative camber case. Positive

camber angle causes that front wheels lie under full load and then the wheels lie in vertical

state.


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To resist fore-aft loads such as acceleration and braking, the arms require two bushings or

ball joints at the body.

At the knuckle end, single ball joints are typically used, in which case the steering loads have

to be taken via a steering arm, and the wishbones look A- or L-shaped. An L-shaped arm is

generally preferred on passenger vehicles because it allows a better compromise of handling

and comfort to be turned in. The bushing in line with the wheel can be kept relatively stiff to

effectively handle cornering loads while the off-line joint can be softer to allow the wheel to

recess under fore-aft impact loads. For a rear suspension, a pair of joints can be used at both

ends of the arm, making them more H-shaped in plan view. Alternatively, a fixed-length

driveshaft can perform the function of a wishbone as long as the shape of the other wishbone

provides control of the upright. This arrangement has been successfully used in the Jaguar

IRS. In elevation view, the suspension is a 4-bar link, and it is easy to work out the camber

gain (see camber angle) and other parameters for a given set of bushing or ball-joint

locations. The various bushings or ball joints do not have to be on horizontal axes, parallel to

the vehicle centre line. If they are set at an angle, then anti-dive and anti-squat geometry can

be dialed in.

In many racing cars, the springs and dampers are relocated inside the bodywork. The

suspension uses a bell crank to transfer the forces at the knuckle end of the suspension to the

internal spring and damper. This is then known as a "push rod" if bump travel "pushes" on

the rod (and subsequently the rod must be joined to the bottom of the upright and angled

upward). As the wheel rises, the push rod compresses the internal spring via a pivot or

pivoting system. The opposite arrangement, a "pull rod," will pull on the rod during bump

travel, and the rod must be attached to the top of the upright, angled downward. Locating the

spring and damper inboard increases the total mass of the suspension, but reduces the

unsprung mass, and also allows the designer to make the suspension more aerodynamic.

2.1.2 Advantages and Disadvantages

Advantages include that it provides the engineer more free parameters than some other types

do. It is fairly easy to work out the effect of moving each joint, so the kinematics of the

suspension can be turned easily and wheel motion can be optimized. It is also easy to work

out the loads that different parts will be subjected to which allows more optimized

lightweight parts to be designed. They also provide increasing negative camber gain all the

way to full jounce travel, unlike the MacPherson strut, which provides negative camber gain

only at the beginning of jounce travel and then reverses into positive camber gain at high

jounce amounts.

The disadvantages are that it may take more space and is slightly more complex than other

systems like a MacPherson strut. Due to the increased number of components within the

suspension setup it takes much longer to service and is heavier than an equivalent

MacPherson design.

http://en.wikipedia.org/wiki/Brake

http://en.wikipedia.org/wiki/Bushing_%28isolator%29

http://en.wikipedia.org/wiki/Drive_shaft

http://en.wikipedia.org/wiki/Jaguar_independent_rear_suspension

http://en.wikipedia.org/wiki/Jaguar_independent_rear_suspension

http://en.wikipedia.org/wiki/Camber_angle

http://en.wikipedia.org/wiki/Bellcrank


http://en.wikipedia.org/wiki/Unsprung_mass

http://en.wikipedia.org/wiki/Kinematics

http://en.wikipedia.org/wiki/MacPherson_strut


25

2.1.3 Uses

The double wishbone suspension was introduced in the 1930s. French carmaker Citroën used

it since 1934 in their Rosalie and Traction Avant models. Packard Motor Car Company of

Detroit, Michigan used it on the Packard One-Twenty from 1935, and advertised it as a safety

feature. Prior to the dominance of front wheel drive in the 1980s, many everyday cars used

double wishbone front-suspension systems or a variation on it. Since that time, the

MacPherson strut has become almost ubiquitous, as it is simpler and cheaper to manufacture.

In most cases, a MacPherson strut requires less space to engineer into a chassis design, and in

front-wheel-drive layouts, can allow for more room in the engine bay.

A good example of this is observed in the Honda Civic, which changed its front-suspension

design from a double wishbone to a MacPherson strut after the year 2000 model.

Double wishbones are usually considered to have superior dynamic characteristics as well as

load-handling capabilities, and are still found on higher performance vehicles. Examples of

makes in which double wishbones can be found include Alfa Romeo, MG, Pontiac, Honda

and Mercedes-Benz. Short long arms suspension, a type of double wishbone suspension, is

very common on front suspensions for medium-to-large cars such as the Honda Accord

(replaced by MacPherson struts in 2013+ models), Peugeot 407, or Mazda 6/Atenza, and is

very common on sports cars and racing cars. It also provides least camber change at bump

and rebound condition.

2.2 HISTORY OF OPTIMIZATION :

Figure: 2.4 Maxima and Minima

Optimization is the act of obtaining the best results under given circumstances. In design, and

maintenance of any engineering system, engineers have to take many technological and

managerial decisions at several stages. The ultimate goal of all such decisions is either to

minimize the effort required or to maximize the desire benefits. Since the effort required or

the benefit desired in any practical situation can be expressed as a function of certain decision

variables, optimization can be defined as the process of finding the conditions that give the

maximum or minimum value of a function.

http://en.wikipedia.org/wiki/Citro%C3%ABn

http://en.wikipedia.org/wiki/Citro%C3%ABn_Rosalie

http://en.wikipedia.org/wiki/Citro%C3%ABn_Traction_Avant

http://en.wikipedia.org/wiki/Packard

http://en.wikipedia.org/wiki/Detroit,_Michigan

http://en.wikipedia.org/wiki/Packard_One-Twenty

http://en.wikipedia.org/wiki/Front_wheel_drive

http://en.wikipedia.org/wiki/Alfa_Romeo

http://en.wikipedia.org/wiki/MG

http://en.wikipedia.org/wiki/Pontiac

http://en.wikipedia.org/wiki/Honda

http://en.wikipedia.org/wiki/Mercedes-Benz


http://en.wikipedia.org/wiki/Honda_Accord

http://en.wikipedia.org/wiki/Peugeot_407

http://en.wikipedia.org/wiki/Mazda_6


26

It can be seen from figure above, that if a point ‘X’ corresponds to the minimum value of

function f(x), the same point also corresponds to the maximum value of the negative of the

function, f(x). Thus, without loss of generality, optimization can be taken to mean

minimization since the maximum of a function can be founded by seeking the minimum of

the negative of the same function. There is no single method available for solving all

optimization problems efficiently. Hence a number of optimization methods have been

developed for solving different types of optimization problems

2.3 FACTOR OF SAFETY:

Factor of safety (FOS), is also known as safety factor (SF), is a term describing the structural

capacity of a system beyond the expected loads or actual loads. Essentially, how much

stronger the system is than it usually needs to be for an intended load. Safety factors are often

calculated using detailed analysis because comprehensive testing in impractical on many

projects, such as bridges and buildings, but the structure’s ability to carry loads must be

determined to a reasonable accuracy.

It is a common practice to size the machine elements, so that the maximum design stress is

below the UTS (Ultimate Tensile Stress) or yield stress by an appropriate factor – the Factor

of Safety. Factor of Safety is used to provide a design margin over the theoretical design

capacity to allow for uncertainty in the design process. Factor of safety is recommended by

the conditions over which the designer has no control that is to account for the uncertainties

involved in the design process. Many systems are purposefully built much stronger than

needed for normal usage to allow for emergency situation, unexpected loads, misuses or

degradation.

There are two distinct uses of safety: One as a ratio of absolute strength (structural capacity)

to actual applied load. This is a measure of the reliability of a particular design. The other use

of FOS is a constant value imposed by law, standard specification, contract or custom to

which a structure must conform or exceed.

2.3.1 Selection of Factor of Safety

The selection of appropriate factor of safety to be used in design of components is essentially

a compromise between the associated additional cost and weight, the benefits if increased

safety or /and reliability. Generally an increased factor of safety results from a heavier

components or a components made from a more exotic material or/and improved component

design. An appropriate factor of safety is chosen based on several considerations. Prime

considerations are the accuracy of load and wear estimates, the consequences of failure, and

the cost of over engineering the components to achieve that factor of safety. For example,

components whose failure could result in substantial financial loss, serious injury or death

usually use a safety factor of four or higher (often ten). Non-critical components generally

have a safety factor of two. Extreme care must be used in dealing with vibration loads, more

so if the vibrations approach resonant frequencies. The vibrations resulting from seismic

disturbance are often important and need to be considered in detail. Where higher factor

might appear desirable, a more thorough analysis of the problem should be undertaken before

deciding on their use.


27

Building commonly uses a factor of safety of 2.0 for each structural member. The value for

buildings is relatively low because the loads are well understood and most structure is

redundant. Pressure vessel use 3.5 to 4.0, automobiles use 3.5, aircraft and spacecraft use 1.2

to 3.0 depending on the application and materials. Ductile, metallic material tends to use the

lower value while brittle materials use the higher values. The field of aerospace engineering

uses generally lower design factors because the cost associated with structural weight are

high (i.e. an aircraft with an overall safety factor of 5 would probably be too heavy to get off

the ground). This low design factor is why aerospace parts and materials are subjected to

very stringent quality control and strict preventive maintenance schedules to help ensure

reliability. A usually applied safety factor is 1.5 but for pressurized fuselage it is 2.0, and for

main landing gear structure it is often 1.25.

2.4 PROBLEM DEFINITION:

The Design of a suspension system is very important because during the journey we generally

face the cushions in the vehicle it is due to the road irregularities such as bumps, pits etc,.

When the vehicle passes on them we experience the sudden motion along with the vehicle, it

is very un comfort to the passengers.

Here, the design of a suspension system comes in to picture. The new design should be such

that, it can withstand / absorb the cushions and it should not transfer those motions to the

passengers. It should posses the smooth and safe ride to the passengers in the vehicle.


28

CHAPTER 3

FINITE ELEMENT METHOD / ANALYSIS (FEM /A)

3.1 Def : FEM is a computer aided numerical method used to obtain solutions for physical

and analytical problems whose behavior is explained by the solution of calculus, linear

algebra, differential equations.

FEM is a -

A numerical method

Mathematical representation of actual problem

Approximate method

3.1.1 Finite - Any continuous object has infinite degrees of freedom & it's just not possible

solve the problem in this format. Finite Element Method reduces degrees of freedom from.

Infinite-to-Finite with the help of discretization i.e. meshing (nodes & elements).

3.1.2 Element - All the calculations are made at limited number of points known as nodes.

Entity joining nodes and forming a specific shape such as quadrilateral or triangular etc is

known as Element. To get value of variable (Say displacement) anywhere in between the

calculation points, interpolation function (as per the shape of element) is used.

3.2 METHODS : There are three methods to solve any engineering problem,

Analytical Method

Numerical Method

Experimental Method

Classical approach.

100% accurate results.

Closed form of solution.

Applicable only for simple

problems like cantilever and

simply supported beams etc.

Complete in itself.

Mathematical representation.

Approximate assumptions

made.

Applicable even if physical

prototype is not available.

Real life complicated

problems.

Results cannot be believed

blindly and must be verified

by experimental methods

Acute measurement.

Time consuming and need

expensive setup

Applicable only if physical

prototype is available.

Results cannot be believed

blindly and min. 3 to 5

prototypes must be tested.


29

Though analytical methods

could also give approximate

results if the solution is not

closed form, but in general

and broad sense, analytical

methods are considered as

closed form solutions

i.e. 100% accurate.

Finite Element Method :

Linear, Nonlinear, Buckling,

Thermal, Dynamic & Fatigue

analysis.

Boundary Element Method:

Acoustics / NVH

Finite Volume Method:

Computational Fluid

Dynamics and Computational

Electromagnetics.

Finite Difference Method:

Thermal and Fluid flow

analysis (in combination with

FVM)

Strain gauge,

Photo elasticity,

Vibration measurements,

Sensors for temp. and

pressure, etc.,

Fatigue test

Table : 3.1

3.2.1 Advantages of FEA: - Visualization increases,

- Design cycle time decreases,

- Reducing Prototypes ,

- Testing time reduction,

- Optimum design.

3.3 ABSOLUTE vs RELATIVE DESIGN:

Relative Design: In industry usually basic design of a category of components remains same

over the years. Say for example existing vehicle power is to be increased from 100 hp to

125hp. Basic design (shape and concept) of components would remain same with minor

changes like scaling the basic design in appropriate proportions. Suppose CAE model &

analysis of the previous version which is performing satisfactorily in the field, is available. If

Analysis of new design (using same element type and size with appropriate loads) shows

stress magnitude less-

than or equal to previous model then it could be concluded that the new upgraded design is

also safe and will perform satisfactorily. This way one can also avoid test correlation for new

model.

Sometimes too much emphasis is given to test correlation & accuracy of the FE model to

minute level. Too much attention to capture each and every detail complicates FE modeling

and analysis unnecessarily (such as modeling bolt threads when main objective is component

design rather than bolt, defining non linear contacts when simple linear connection can work

or dense mesh in the name of accuracy without due consideration for hardware and software

capabilities etc.).

Absolute Design: This approach is useful when the product / component is designed for the

first time 'i.e. innovative design and no previous record of similar product is available. The


30

design engineer himself not very sure about boundary conditions & various load cases. CAE

results of such a design must be verified properly via testing and FE model should be

corrected in case of variation in the test & FEA results.

3.4 THEORETICAL FINITE ELEMENT ANALYSIS:

Theory course deals mainly with

- Various methods to derive stiffness matrix [K]

- Assembly of [K]

- Solution techniques

Element Stiffness Matrix

Stiffness matrix is like password or PIN to the treasury of FEA.

[K] stiffness matrix, the characteristic property of element depends on geometry as well as

material.

Direct Method - Easy to understand but difficult to program. It is not used for commercial

software code generation.

Variation Method - Rayleigh- Ritz Method : difficult to understand moderate from code

writing point of view.

Weighted Residual Method - Galerkin Method : difficult to understand but easy from

programming point of view. This method is used in most of the commercial software’s.

3.5 SOFTWARE BASED FEM: For using any commercial software there are 3 steps –

- Pre-processing- Consumes most the out of the three steps.

- Processing (or solution) - just click on "Solve"& it's the software's turn to do the job.

- Post-processing- Result viewing & interpretation.

Step 1 - Pre processing

- CAD data

- Meshing (or discretization to convert infinite dof to finite one)

- Boundary conditions

In early stage of industrial applications of Finite Element Analysis, CAD, meshing and

analysis al1used to be carried out by a single engineer only. Soon it was realized that

separation of the jobs and forming dedicated subgroups i.e. CAD group, Meshing group &

Analysis or calculation group is necessary for optimum output and efficiency.

CAD & Meshing -There are specialized software’s for CAD, Meshing & Analysis. CAD and

meshing consumes most of the time. For example - Typical time for a single person to mode1

(CAD) four cylinder engine block is 6 weeks & for brick meshing 7 weeks (For tetra mesh

about 2 weeks). Boundary Conditions - Consumes least time but it is the most Important step (typically

applying10 load cases is about 1 day job). Three months hard work of meshing & CAD data

preparation of engine block would be undone in just one day if boundary conditions are not

applied properly. After completion of preprocessing i.e. CAD, Meshing and Boundary


31

conditions, software internally forms mathematical equations of the form [F] = [ K] [µ]

.

Step 2 - Processing or Solution

During preprocessing user has to work hard while solution step is the turn of

computer to do the job. User has to just click on solve icon. Internally software carries out

matrix formations, inversion, multiplication & solution for unknown e.g. displacement &

then find strain and stress for static analysis.

Today we are using FEA just because of availability of computers. FEM has been known to

mathematicians and engineers right from late 50's but since solving so many equations

manually was not possible, in true sense FEA got recognition only after emergence of high

capacity computers.

Step 3 - Post processing

Post processing is viewing results, verifications, and conclusions & thinking about

what steps could be taken to improve the design.

3.5.1 Practical Applications of FEA

CAE group responsible for FEA related activities, receive following types of job orders

- New design

- Optimization or cost cutting projects

- Failure analysis

3.5.1.1 New Design

New or innovative kind of design is a real challenge for design engineer. In automobile

industry, when new version of existing vehicle is launched (upgraded version), most of the

components are quite similar to the existing one (scaled proportionately). Innovative kind of

components is usually not more than 15 %.

At least initial run of this category of job is easy for CAE engineer. Sit with design and test

engineer to decide boundary conditions and then run the analysis. Real work starts only when

the prototype is prepared and test & FEA result correlation process is initialized. After

achieving correlation various permutations and combinations could be carried out to make the

product better and optimum from cost as well design point of view.

3.5.1.2 Cost Cutting or Optimization Projects

At the moment Indian Auto sector is experiencing a boom but from 1995 to 2003 there was a

slack. During the period most of industries were busy with cost cutting measures for their

survival.

In Indian market till late 80% same kind of vehicles were running on the road without any

change. These designs were transferred to Indian companies in 50's & 60's from their

overseas collaborators. Design philosophy was different at that time i.e. design for infinite

life. But slack in the market and emergence of new tools like CAD/CAM/CAE, new cost

efficient manufacturing techniques and availability of low cost materials forced auto

manufacturers to adapt to the changing circumstances via optimization of design. Suppose

selling price of the product is Rs.100 & actual manufacturing cost is Rs. 60. Reduction of

cost even by say Rs.1 by using CAD / CAM / CAE (reduction in thickness, change in

material etc.) will result in lot of profit for the company.


32

3.5.1.3 Failure Analysis: Warranty: Every company offers warranty on its product. Company is under legal binding to

replace the component failing within warranty period, free of cost. It is not only additional

cost which is incurred but also bad name to the product and company. Probable reasons of failure:

- Improper process

- Manufacturing defects

- Faulty material

- Environmental conditions

- Weather

- Road condition

- Design abuse

- Genuine Design problem

3.6 TYPES OF ANALYSIS: - Linear Static Analysis

- Dynamic Analysis

- Modal Analysis

- Buckling Analysis

3.6.1 Linear Static /Structural analysis

- Used to determine deformation, stresses, strain, and reaction forces.

- Used for static loading conditions.

- Nonlinear behavior such as large deflection, large strain, contact, plasticity, hyper

elasticity, creep can be simulated.

3.6.2 Dynamic Analysis:

Structural dynamic analysis, a subset of pure structural analysis, covers the behavior of

structures subjected to dynamic loading. Dynamic loads include everyday activities which

people are accustomed to, but which still have an overall effect upon a structure. Cultural

events are those that are expected and taken for granted by the building occupants, such as

daily walking on a floor, exterior wind causing movement in tall structures, motion created

by elevators and traffic. Cultural events can be man-made or natural, ranging from waves and

earthquakes to pile driving, vibratory compaction and blast-induced ground vibration. Any

structure can be subject to dynamic loading from such events, raising concerns for the

occupants. By employing dynamic analysis, I can find structure displacements, velocity, or

acceleration time histories, and this data can be used to evaluate the structural behavior

during the application of dynamic loads.

Dynamic analysis for simple structures can be carried out manually, but for more complex

structures, GeoSonics / Vibra-Tech professionals use finite element analysis techniques to

calculate the dynamic properties of structure such as mode shapes and natural frequencies.

These techniques provide the answers for modifications of floor and wall systems to stiffen

and strengthen the structure to reduce response.


33

3.6.3 Modal Analysis

The goal of modal analysis in structural mechanics is to determine the natural mode shapes

and frequencies of an object or structure during free vibration. It is common to use the finite

element method (FEM) to perform this analysis because, like other calculations using the

FEM, the object being analyzed can have arbitrary shape and the results of the calculations

are acceptable. The types of equations which arise from modal analysis are those seen in

Eigen systems. The physical interpretation of the Eigen values and eigenvectors which come

from solving the system are that they represent the frequencies and corresponding mode

shapes. Sometimes, the only desired modes are the lowest frequencies because they can be

the most prominent modes at which the object will vibrate, dominating all the higher

frequency modes.

It is also possible to test a physical object to determine its natural frequencies and mode

shapes. This is called an Experimental Modal Analysis. The results of the physical test can be

used to calibrate a finite element model to determine if the underlying assumptions made Ire

correct (for example, correct material properties and boundary conditions are used).

3.6.4 Buckling Analysis

Figure : 3.1 a & b Buckling analysis

- Applicable for only compressive load,

- Slender beams and sheet metal parts,

- Bending stiffness and Axial stiffness,

- Large Lateral deformation.

Output from software: Critical value of load.

Practical applications: Vacuum vessel, long gear shifter rod analysis etc.,

3.7 OPTIMIZATION - Geometrical Parameters,

- Shape Optimization.

Geometrical Parameters:

- Optimization for geometry parameters, work well at individual component level

rather than complicated assemblies.

- Software can not add or remove geometry on its own but can play with only pre

defined parameters within specified limits.


34

Shape Optimization:

- Usually restricted to only linear static & normal mode dynamics.

- Good tool for innovative kind of products (when initial shape to start with is not

known or fixed).

- Software can give hint for addition or removal of geometry.

Practical applications: Applicable to any component which is over or under designed.

3.8 ENGINEERING APPLICATIONS OF OPTIMIZATION:

Optimization in its broadest sense can be applied to solve any engineering problem.

To indicate the wide scope of the subject, some typical applications from different

engineering disciplines are given below.

Design of aircraft and aerospace structures for minimum weight.

Finding the optimal trajectories of space vehicles.

Design of civil engineering structures such as frames, foundations, bridges, towers,

chimneys and dams for minimum costs.

Minimum-weight design of structures for earthquakes, wind and other types of

random loadings.

Design of water resources systems for maximum benefits.

Optimal plastic design of structures.

Optimal design of linkages, cams, gears, machine tools and other mechanical

components.

Selection of machining conditions in metal-cutting processes for minimum production

costs.

Design of material handling equipment such as conveyors, trucks, and cranes for

minimum cost.

Design of pumps, turbines and heat transfer equipment for maximum efficiency.


35

CHAPTER 4

SOFTWARE REVIEW

4.1 HYPERMESH V11 :

Altair Hyper mesh is a high-performance finite-element pre-processor for popular finite-

element solvers that allows engineers to analyze product design performance in highly

interactive and visual environment.

Hyper Mesh’s user interface is easy to learn and supports a number of CAD geometry and

finite-element model file formats, thereby increasing interoperability and efficiency.

Advanced functionality within Hyper Mesh allows user to efficiently manipulate geometry

and mesh highly complex models. These functionalities include extensive meshing and model

control, morphing technology to update existing meshes to new design proposals and

automatic mid-surface generation for complex designs with varying thicknesses. Solid

geometry enhances tetra-meshing and hexa-meshing by reducing interactive modeling times,

while batch meshing enables large scale meshing of parts with no manual clean-up and

minimal user input.

4.1.1 Benefits of Hyper mesh:

Open-Architecture Design - With the broadest set of direct CAD and CAE interface

coupled with user defined integration, Hyper mesh fits seamlessly within any

simulation environment.

High-Speed, High-Quality Meshing - With both automatic and semi-automatic

shell, tetra- and hexa-meshing capabilities. Hyper mesh simplifies the modeling

process of complex geometries.

Advanced Model Morphing - A flexible set of morphing tools allows user to modify

existing meshes to meet new designs and reduce model development costs.

Increases End-User modeling Efficiency - Batch mesher technology eliminates the

need to perform manual geometry clean-up and meshing, thus accelerating the model

development process.

Reduce Training Time and Cost through Elimination of Redundant Tools - An

easy-to-use, intuitive graphical user interface makes it simple for anyone to learn the

software, which further increases modeling efficiency and reduce cost.

Reduce Model Assembly Time - Leverage highly Automated methods for rapid

model assembly that create connection such as bolts, spot welds, adhesive and seam

welds.

4.1.2 Meshwork Morpher:

It is a path breaking advanced CAE software developed by Detroit Engineered Products

(DEP) that:

Allows user to rapidly morph an existing FE / CFD mesh to an intended target shape.

It can used very effectively to reduce product development time.


36

Convert regular FE/CFD models to intelligent parametric FE/CFD models and

enables optimization using the parameterized models.

Helps to create quick concept models by cutting, morphing, blending & stitching

existing structural FE meshes.

Enables automated re-meshing & re-assembly after morphing- structural &CFD

models.

Provides Advanced Morphing functions such as fillet radius morphing, pattern

morphing etc.

Allows user to handle very large scale CFD models using Morphing view for

parameterization and optimization studies.

4.2 RADIOSS:

Altair Radioss is a multidisciplinary finite element solver developed by Altair Engineering. It

can solve both linear and non-linear problems. It is a state-of-the-art finite element solver

uniting implicit and explicit integration schemes for the solution of a wide variety of

engineering problems, from linear statics and linear dynamics to complex nonlinear transient

dynamics and mechanical systems. This robust, multidisciplinary solver enables designers to

maximize performance related to durability, NVH, crash, safety, manufacturability, and fluid-

structure interaction, in order to bring innovative products to market faster.

RADIOSS is comprehensive analysis capabilities for linear and non-linear finite element

analysis, sheet metal stamping, and multi-body dynamics are accessible via two input

formats.

4.2.1 Benefits

Structural Simulation -

Easily simulate dynamic loading events including crash, shock, impact, earthquake,

wave propagation, etc.

Linear and nonlinear vibration analysis (modal and frequency domain)

Linear and nonlinear static analysis

Preferred Crash and Safety Performance Solution RADIOSS includes a broad,

correlated set of barriers, impactors, and occupant models. Coupled with Hyper

Crash, RADIOSS provides a highly-tuned and automated crash simulation

environment.

4.3 HYPERVIEW :

Altair Hyper view is a complete post-processing and visualization environment for finite

element analysis, multi-body system simulation, digital video, and engineering data. Hyper

view combines advanced animation and XY plotting features with window synching to

enhance results visualization. Hyper view also saves 3D animation results in Altair's compact

H3D format, so users can visualize and share CAE results within a 3D Ib environment using

Altair Hyper View Player. Amazingly fast 3D graphics and unparalleled functionality set a

new standard for speed and integration of CAE results post-processing. Coupling these

features with Hyper view’s advanced process automation tools dramatically improves results

visualization and reporting.


37

4.3.1 Benefits Hyper view is a complete visualization environment for FEA, CFD, and multi-body

system simulation data.

Through a complete, extendable library of direct model and results readers, users can

post-process any CAE analysis.

Hyper view’s animation capabilities and speed make it ideal for working with

extremely large models and results files.

A multi-window, multi-page environment enables users to study several model

configurations simultaneously.

To check for correlations between two models or simulation and reality, results can be

overlaid with a model or video within the same window.

The Results Browser enables users to efficiently navigate though complicated models.

The Results View gives quick access to all analysis results. Plot styles help to

efficiently generate contour plots based on common settings.

Results Math is a powerful tool to generate new results from existing simulations by

using mathematical expressions or external scripting languages. Time consuming

result manipulation tasks can be performed in batch using HVTrans and saved in

H3D.

All post-processing sessions can be stored in a session file or a report template.

Session files help to reopen a complete session spanning across multiple pages and

applications. Report templates similarly reopen previous sessions but can be used to

generate sessions for model variations or similar simulations.

Users can explore CAE models with Hyper view’s in-depth model and results

interrogation tools that are based on user-defined criteria.

Hyper view’s synchronization capabilities help users gain insight into model integrity

and behavior. This allows users to synchronize and visualize FEA results, multi-body

systems results, XY plotting (simulation or test data) and digital video data.

Hyper view enables users to share CAE results within a 3D Ib environment or

Microsoft PowerPoint using Altair Hyper view Player® via Altair’s compact .h3d

file.

Export Hyper view session reports directly to HTML or PowerPoint including text,

images, AVIs and .h3d files.

Users can create custom model views such as section cuts and exploded views by

combining functionality from Hyper view’s comprehensive post-processing tool and

utility set.

Hyper view contains Hyper Graph, a powerful XY plotting and data analysis package

that is tightly integrated within the Hyper view environment.

Hyper view contains a completely open environment that enables users to expand the

post-processing toolset in virtually any way. Users can:

Generate plot macros to capture and replay often-used

mathematical curves.

Create custom math functions and algorithms.

Completely customize the GUI to cater to the user’s

preferences and needs.

Automate any post-processing procedure and embed logical control through the

command layer and Tcl / Tk programming.

Automate the generation and presentation of standard animations, plots and tables, as

Ill as quickly compare results and correlation studies using the Overlay Results

option.


38

CHAPTER 5

PRE-PROCESSING

5.1 Initial Geometry Of A Double Wishbone Suspension System :

Figure : 5.1 Geometry of a double wishbone

This is a full model of a front / rear double wishbone suspension system. Hence we know that

the car having a four wheels which has two double wishbone suspension systems at each

wheel (front / rear). Therefore we have four wishbone suspension systems at each wheel for a

car all of them are similar to each other. So we can carry out the analysis for any one of them.

The first step is to split the above system in to half and remove the excess components like

tire, differential, rim etc. By removing all the unnecessary parts from the system it would be

as figure 5.2. The wishbone suspension system consists of rear suspension, spring, wheel hub,

upper control arm and lower control arm.


39

Figure : 5.2 Wishbone setup

5.2 MATERIAL PROPERTIES :

Upper & lower arms has to withstand high load carrying capacity. so we need higher the

yield point, elasticity, buckling strength, etc. So we choose the material is STEEL, which is

having all these characters.

Table : 5.1

DENSITY (ρ)

7.85e-6

kg/mm3

ELASTIC MODULUS (E)

190-210 Mpa

POISSION’S RATIO (μ)

0.27-0.3

TENSILE STRENGTH

276 -1882 Mpa

YIELD STRENGTH

186 -758 Mpa


40

5.3 MESH GENERATION :

Mesh generation plays an important role in obtaining valid results. Mesh should be refined at

the wheel hub as the most of the load is taken by the hub. Mesh is also refined near the

joining of the components, change of cross sections as the stress concentration is more at

these places. The finite element modeling is carried using hypermesh v11.

5.3.1 Types of Meshing:

5.3.1.1 1D Meshing

One of the dimension is very large in comparison to rest of the two.

Element Shape : Line

Elements Type : Rod, Bar, Beam, Pipe, Axisymmetric shell etc.

Practical Application : Long shafts, beams, pin joints, connection elements

.

Figure : 5.3 1D Meshing

5.3.1.2 2D / Surface Meshing

Two of the dimensions are very large in comparison to third one. X, Y are comparable and Z

is negligible.

Element Shape : Quad, Tria.

Element Type :Thin shell, plate, membrane, plane stress, plane strain, axi-symmetric solid

etc.

Practical Application : Sheet metal parts, plastic components like instrument panel etc.

5.3.1.3 3D / Solid Meshing

All dimensions are comparable.


41

Figure : 5.4 3D / Solid Meshing

Element Shape : Tetra, Penta, Hex, Pyramid.

Element Type : Solid

Practical Applications : Gear box, Engine block, Crankshaft etc.

Meshing the Components:

Meshing is done individually for each component.

Criteria for Meshing -

Element type

R - Trais

Mesh type

Tetra

Target Element Size

4

Min. Element Size

1

Tet collapse

0.2

Skew

75

Jacobean

60

Table 5.2

Meshing the components wheel hub, spring, rear suspension, upper control arm and lower

control arm with the above criteria.


42

Figure : 5.5 Wheel hub

Figure : 5.6 Suspension spring


43

Figure : 5.7 Rear Suspension

Figure : 5.8 Upper control arm


44

Figure : 5.9 Lower control arm

Now assembling all these components to form a complete suspension system.

Figure : 5.10 Assembly of Double Wishbone

Creating 1D Elements :

1D elements are created to combine the two components (straight beams) and to give the

connectivity to the elements at wholes (wagon wheel beams).


45

Creation of Straight Beams :

Measure the radius of the whole where beam is to be created, and create a property of a beam

with that radius. Create a center of the whole along the no. of elements along the whole; join

these points in a indirection.

Creation of Wagon wheel Beams :

Measure the surface area of the whole say X, count the no. of node along the whole say Y,

equating X and Y to the area of the circle ( ).

i.e. = X / Y,

From this equation we have to find the radius ‘r’, and create a property of a beam with this

radius. Create a circle center of a whole and join the nodes of the elements in circular path,

translate this wagon wheel beam along the whole.

Figure : 5.11 straight beams


46

Figure : 5.12 Wagon wheel beams

5.4 BOUNDARY CONDITIONS AND LOADING:

The assembly of a suspension system is constrained at rear end suspension in order to avoid

vibrations during analysis i.e, it may fly off from the space during analysis, in order to avoid

this, rear suspension of rear surface is constrained in all six degree of freedoms (Ux, Uy, Uz,

Rx, Ry, Rz).

Spring suspension is constrained at one and three degree of freedoms (i.e, Ux, Uz). so that it

may not move in X and Z directions respectively. To achieve valid results boundary

conditions are considered.

Force Applied = 100N

Constraints are applied at backside of the rear suspension

UX, UY, UZ, RX, RY, RZ = Arrested

For spring constraints are applied on the surface with one and three Degree of freedom i.e,

Ux, Uz = Arrested


47

Figure : 5.13 Constraints Six Dofs at rear suspension

Figure : 5.14 Constraints 1 & 3 Dofs on the spring


48

5.4.1 Loading :

In order to calculate the actual load transfer in the system, a 100N dummy dynamic load is

applied at the wheel hub to test the whole system for accuracy. A test run is carried out to

validate the results. By these results the actual load is calculated, it well defined in upcoming

chapter.

Figure : 5.15 Loading


49

CHAPTER 6

PROCESSING

Optimization of any component takes a lot of time and need skilled team to develop a

modified component. It takes nearly eight to fifteen months. During this period the team

investigates the whole system for modifications such as type of material to be changed,

thickness, avoiding excess parts in the components, reducing weight etc.

Due to the time consideration, lack of industrial experience I’m unable to optimize the full

modal. With my exposure to Hypermesh, I concentrated only on optimization of Upper

control arm. It took for me more than four months to optimize the control arm apart from

learning Hypermesh software. To check for the displacement of the elements should be in

first order trias and for optimization the elements are changed to second order trias.

6.1 SET UP FOR DESIGN SPACE :

Figure : 6.1 Setup for Design Space

Bluish color represents the non design part (front and rear). This part is meshed with the 3D

elements (tetra mesh). In between these parts i.e, pink and yellow color mesh (2D mesh with

R-Trais) represents the design space. The yellow color forms a medium between the 2D and

3D mesh. The design space is going to optimize the arms for thickness, weight, strength,

stress etc.


50

6.2 LOAD CALCULATION FOR UPPER CONTROL ARM :

Previously we applied 100N dummy dynamic load for the system. Repeat the same process

for this system (include modified control arm).

Figure : 6.2 Assembly of Modified Control Arm

With this 100N force acting on the wheel hub, we have to find out the force distribution at

upper control arm. It is well calculated by the control cards. Control card is used to display

the output forces for the request elements / nodes. The request elements / node are created in

separate sets for both elements / nodes. We selected two node at the upper control arm

(1045060, 1045061).

Loads at given nodes : The force distribution at the respective nodes for 100N. Scale the below values with the

actual car load.

Node: 1045060 X: 20.43,

Y: 25.41,

Z: 3.35.

Node: 1045061

X: -45.11,

Y: -6.659,

Z: -12.07.


51

6.2.1 Load Calculations

Assuming the dead weight of a car is about 3.5 tons. Now considering five passengers

capacity of a car, each passenger average weight is about 100kgs.

Dead wt. of a car = 3.5 ton

Wt. of a passenger = 100kgs

Tot. no. of passengers = 5 no’s

Tot. weight of a passengers = 5× 100 kgs

= 500 kgs / 0.5 ton.

Tot. Weight of a car = Dead wt. of a car + Tot weight of passengers

= 3.5 + 0.5 ton

= 4 ton

This four ton weight is distributed equally at each wheel with one ton weight (i.e 1000kg).

Converting this weight in to kgs

1kg = 9.8N

1000kgs = 9800N

Approximately = 10000N.

The force distribution at the given nodes (1045060, 1045061) for 10000 N is calculated as

below.

Node: 1045060

X: 20.43 at 100 N.

X : ? at 10000N.

i.e., X = 2043,

Similarly, Y = 2541,

Z = 335 .

Node: 1045061

X = - 4511,

Y = 6659,

Z = - 12.07.

Now applying these force at nodes 1045060, 1045061 with respect to the X, Y, Z axis

respectively.

Applying these forces at respective nodes run the analysis for varied thickness for design

space for linear static analysis, buckling analysis, modal analysis. These analysis are

performed at varied thickness are discussed in detailed in upcoming chapter.


52

Figure : 6.3 Force at node 1045060

Figure : 6.5 Force at node 1045061


53

CHAPTER 7

ANALYSIS

7.1 LINEAR STATIC ANALYSIS :

It is the simplest and most commonly used type of analysis.

Figure : 7.1 Stress – Strain Curve for Linear Static

7.1.1 Linear :

Linear means straight line. σ = ɛ E is equation of straight line (y = m x) passing through

origin."E" Elastic Modulus is slope of the curve & is a constant. In real life after crossing

yield point material follows non liner curve but software follows same straight line.

Component brake into two separate pieces after crossing ultimate stress but software based

analysis never show failure in this fashion. It shows single unbroken part only with red color

zone at the location of failure.

Analyst has to conclude whether the component is safe or fail by comparing the max. Stress

value with yield or ultimate stress.

7.1.2 Static : There are two conditions for static analysis

1) No variation of force with respect to time (dead weight)


54

Figure 7.2 : Force vs Time

2) Equilibrium condition - ∑Force = 0, ∑Moments = 0

∑Fx= 0, ∑Mx= 0,

∑Fy= 0, ∑My= 0,

∑Fz= 0, ∑Mz= 0.

The upper control arm is carried linear static analysis at varied thickness of the material at

design space for six iterations from 15mm to 10mm thickness. By applying calculated load

for 10000N in X, Y, Z axis respectively at the given nodes (1045060, 1045061).

7.1.3 Linear Static Analysis before optimization (15mm Thickness) :

In initial volume, displacement of the upper arm is 9.2e5 mm

3 and 3.44 mm respectively. This

displacements is higher than their loads. So I reduce the displacement by reducing the volume

of the upper arm.

Figure : 7.3 Displacement

Before optimization, displacement is high


55

So the life time should affect

Displacement is high in applied area

The material can easily to reach out the yield point

So I reduce the displacement value in same load condition

Figure : 7.4 Von-Misses stress

In before optimization, the stress plots are shown in fig.7.3. This plots to give a value of

amount of stress concentration. Where ever the stresses are too low, that places should reduce

the amount of volume. This reduction of volume to reduce the displacement in previous load

condition. Blue color represents the low stress value and red color is high stress value.

Figure : 7.5 P1 Major (Tension)

In this stress plots to gave a new ideas for optimization process. Where ever the stress value

is too low that particular area can be reduced.

Tensile force is only on the strips & load carrying places

This force only express the elongation of the control arm

This elongation only affect the life time of the control arm


56

Figure : 7.6 P3 Minor (Compression)

Compression is only for the two side of the wishbones

So that two wishbones are compressed by force

Arm goes to lower position to initial position compression takes place

This compression is low level in wishbone

7.1.4 Linear Static Analysis after optimization (10mm Thickness) :

Figure : 7.7 Displacement

This is the displacement plot about X axis. This value is compare to the previous value

difference are there in the places, because I reduce the material from the previous component.


57

Figure : 7.8 Von – Misses stress

In this plot to explain the overall stress on the material. This stress values are seen in fig. In

strips stresses are too low, but I consider the connectivity of the component with strips and

two wishbones. In two wishbones where ever the stresses are low that particular area the

material can remove. I take a parameters in direct software.

Figure : 7.9 P1 Major (Tension)

Tension can be reduced compare to the previous analysis

Model can resist tensile force

So that the model can get the life time than the previous model

Figure : 7.10 P3 Minor (Compression)


58

Compression is reduced in left side of the wishbone

So that the model can be improved their quality

Also improved the life time

7.2 BUCKLING ANALYSIS :

Buckling is a mathematical instability, leading to a failure mode. Theoretically, buckling is

caused by a bifurcation in the solution to the equations of static equilibrium. At a certain

stage under an increasing load, further load is able to be sustained in one of two states of

equilibrium: an under deformed state or a laterally-deformed state.

In practice, buckling is characterized by a sudden failure of a structural member subjected to

high compressive stress, where the actual compressive stress at the point of failure is less than

the ultimate compressive stresses that the material is capable of withstanding. For example,

during earthquakes, reinforced concrete members may experience lateral deformation of the

longitudinal reinforcing bars. This mode of failure is also described as failure due to elastic

instability. Mathematical analysis of buckling makes use of an axial load eccentricity that

introduces a moment, which does not form part of the primary forces to which the member is

subjected. When load is constantly being applied on a member, such as column, it will

ultimately become large enough to cause the member to become unstable. Further load will

cause significant and somewhat unpredictable deformations, possibly leading to complete

loss of load-carrying capacity. The member is said to have buckled, to have deformed.

7.2.1 Buckling Analysis before Optimization (15mm Thickness):

Figure :7.11 Mode 1

http://en.wikipedia.org/wiki/Structural_failure

http://en.wikipedia.org/wiki/Bifurcation_theory

http://en.wikipedia.org/wiki/Mechanical_equilibrium

http://en.wikipedia.org/wiki/Stress_%28mechanics%29

http://en.wikipedia.org/wiki/Elastic_instability

http://en.wikipedia.org/wiki/Elastic_instability


59

Figure :7.12 Mode 2

Figure :7.13 Mode 3

Figure :7.14 Mode 4


60

Figure :7.15 Mode 5

7.2.2 Buckling Analysis after Optimization (10mm Thickness):

Figure :7.16 Mode 1

Figure :7.17 Mode 2


61

Figure :7.18 Mode 3

Figure :7.19 Mode 4

Figure :7.20 Mode 5


62

7.3 MODAL ANALYSIS :

Modal analysis is the study of the dynamic properties of structures under vibration excitation.

Modal analysis is the field of measuring and analyzing the dynamic response of structures

and or fluids when excited by an input. Examples would include measuring the vibration of a

car's body when it is attached to an electromagnetic shaker, or the noise pattern in a room

when excited by a loudspeaker. Modern day modal testing systems are composed of

transducers (typically accelerometers and load cells), or non contact via a Laser micrometer,

an analog-to-digital converter frontend (to digitize analog instrumentation signals) and a host

PC (personal computer) to view the data and analyze it.

Classically this was done with a SIMO (single-input, multiple-output) approach, that is, one

excitation point, and then the response is measured at many other points. In the past a

hammer survey, using a fixed accelerometer and a roving hammer as excitation, gave a MISO

(multiple-input, single-output) analysis, which is mathematically identical to SIMO, due to

the principle of reciprocity. In recent years MIMO (multi-input, multiple-output) has become

more practical, where partial coherence analysis identifies which part of the response comes

from which excitation source.

Typical excitation signals can be classed as impulse, broadband, spite sine, chirp, and

possibly others. Each has its own advantages and disadvantages. The analysis of the signals

typically relies on Fourier analysis. The resulting transfer function will show one or more

resonances, whose characteristic mass, frequency and damping can be estimated from the

measurements.

It is also possible to test a physical object to determine its natural frequencies and mode

shapes. This is called an Experimental Modal Analysis. The results of the physical test can be

used to calibrate a finite element model to determine if the underlying assumptions made Ire

correct (for example, correct material properties and boundary conditions are used).

7.3.1 MODAL ANALYSIS BEFORE OPTIMIZATION (15 mm Thickness):

Before starting the analysis we have to select EIGRL force for modal analysis, we have to

choose minimum three roots to find the effect of stress completely on the arms. So we choose

five roots for the analysis for varied thickness of design space.

Contour plots of modal analysis for 15mm thickness.

Figure : 7.21 Mode 1


63





64


7.3.2 MODAL ANALYSIS AFTER OPTIMIZATION (10 mm Thickness):




65


Figure : 7.29 Mode



66

CHAPTER 8

POST-PROCESSING

8.1 Comparison of results - Linear Static Analysis :

Thickness ‘mm’

15

14

13

12

11

10

Displacement

in ‘mm’

3.44

3.47

3.5

3.54

3.58

3.64

Von-Misses

stress

42

44

47

50

54

59

P1Major

(Tension)

42

45

48

50

54

59

P2 Minor

(Compression)

6.3

6.5

7.3

8.4

9.6

11

Table :8.1

8.2 Buckling Analysis:

Thickness ‘mm’

15

14

13

12

11

10

Mode 1 in ‘Hz’

-177

-177

-175

-173

-172

-161

Mode 2 in ‘Hz’

-347

-341

-347

-347

-347

231

Mode 3 in ‘Hz’

354

354

354

353

352

234

Mode 4 in ‘Hz’

-355

355

-355

-354

-353

271

Mode 5 in ‘Hz’

363

364

364

364

365

276

Table : 8.2


67

8.3 Modal Analysis:

Thickness ‘mm’

15

14

13

12

11

10

Mode 1 in ‘Hz’

80

81

28

85

85

87

Mode 2 in ‘Hz’

384

386

96

368

388

389

Mode 3 in ‘Hz’

563

568

135

542

584

590

Mode 4 in ‘Hz’

1023

1011

288

968

973

959

Mode 5 in ‘Hz’

1338

1352

376

1289

1400

1419

Table : 8.3

8.4 Upper control arm Thickness vs Volume:

Thickness ‘mm’

Volume mm3

Total mass

15

924668.4

7.305e-3

14

863023.84

6.818e-3

13

801379.28

6.331e-3

12

739734.72

5.844e-3

11

678090.16

5.357e-3

10

616445.6

4.87e-3

Table : 8.4


68

8.5 CALCULATION OF FACTOR OF SAFETY:

According to the Theory of Failure the Factor of Safety is defined as the ratio of Ultimate

Tensile Strength of the material to the maximum Von-Mises Stress.

Factor of Safety = Ultimate Tensile Strength (Mpa) / Maximum Von-Mises Stress.

Factor of Safety = 841Mpa / 231.552 Mpa.

According to the Automotive Industry Standards Committee (AISC) the factor of safety for

automobile components is specified as 3.5 and the factor of safety for the proposed upper

control arm of suspension system is 3.49 is very nearer to the desired value, here all the

stress, deformation and factor of safety of the proposed upper control arm is within the limit

of permissible values, hence the design is considered to be optimum.

The weight of the proposed upper control arm is 4.83Kg.

The percentage of weight reduction is 39.5% i.e. 40%.

8.6 ECONOMIC CONSIDERATIONS:

1kg of carbon steel rate in global market = Rs 60

Weight of upper control arm

Before Optimization = 7.25 Kg

After Optimization = 4.83 Kg

Total reduction in weight = 2.87 kg

Reduction of weight give savings = Rs.145

Each car having four wheels. It means there are four (4 No’s) uppercontol arms

= Rs 145× 4

= Rs 580 per car.

Average cars roll out for market = 1 lakh cars

= 4 lakh upper control arms

= 4 00 000 × 580

= 23 Crore 20 Lakhs Savings.

8.6.1 Fixed cost:

Weight saving per upper control arm = 2.87Kg

No. control arms per car = 4

weight savings per car = 4 × 2.87

= 11.48 kg

Cost of steel = Rs 60

Fixed cost savings per car = 60 × 11.48

= Rs 688.8


69

Market rollout of cars per annum globally = 1 Lakh cars

Annual savings in manufacturing cost = 688.8 × 1 Lakh

= Rs 688.8 Lakhs

= Rs 6 crores 88 lakhs 80 thousands

8.6.2 Operational Cost:

Average ideal weight of a car (WoC) = 3.5 Tons

= 3500 Kgs

Ideal Mileage of a car (MoC) = 20 Kms per liter

Global average diesel price per liter (Pd) = Rs 55

Fuel cost per Km per kg = (Pd x MoC) / WoC

= (55× 20) / 3500

= Rs 0.314

Average travel of a car per day = 200 Kms

Average travel of a car per annum = 73 000 Kms.

Cost savings per car per annum = 73 000 × 0.314

= Rs 22, 922

Market presence of car = 1 Lakh cars

Overall cost savings per annum on all the cars = 1 Lakh × 22, 922

Total Savings per annum through this project = Rs 229 Crores 22 Lakhs.

8.7 ADVANTAGES OF OPTIMIZED MODEL

In comparison of features, displacements are reduced, and also compare the stress

plots, stresses are increased

So that component has low displacement & high stress can increase the life time of

the component.

If the life time can increase, usage of the component level can increase.

Rate of Manufacturing amount can increase .

Cost of manufacturing can reduce.

Savings of manufacturing cost can increase.

In annual rate of savings is Rs.299 Crores 22 Lakhs.


70

CHAPTER 9

SUMMARY AND CONCLUSION

9.1 SUMMARY OF EXISTING CONTROL ARM:

Output parameters

Value

Factor of Safety

Von-misses stress

143.506 N/mm2

5.64

Deformation in X-direction

0.438 mm

Deformation in Y-direction

3.43 mm

Deformation in Z-direction

0.002016 mm

Weight of Upper control arm

7.25 Kg

Table : 9.1

9.2 SUMMARY OF PROPOSED CONTROL ARM:

Output parameters

Value

Factor of Safety

Von-misses stress

231.552 N/mm2

3.49

Deformation in X-direction

0.45 mm

Deformation in Y-direction

3.624 mm

Deformation in Z-direction

0.00206 mm

Weight of Upper control arm

4.83 Kg

Table : 9.2


71

9.3 CONCLUSION :

This optimized process successfully finished by using HYPERMESH, HYPERVIEW, to run

the analysis in RADIOSS software. This optimization method to give a innovative problems

and rectified the problem by using this software. This optimized model is very useful to

manufacturing industrial development. This optimized model should give more advantages

for manufacturing industry. It gives more life time compare to the previous model, cost

reduction, material reduction; reduce the man power of the production.

The weight of the existing upper control is found to be 7.25 Kg and after design

optimization the weight of the proposed upper control arm has come to a weight of

4.83 Kg. The percentage of weight reduction is 39.5%.

As the factor of safety for the proposed upper control arm subjected to loading is 3.49

which is desired value, the design is optimum.

Also, as the Von-Mises stress obtained in upper control arm is found to be 231.552

N/mm2

which is within the limits of permissible yield strength of 250 N/mm2, the

design is acceptable.

9.4 FUTURE SCOPE OF WORK:

The three analysis’s linear static, buckling, modal can be performed to lower control arm,

wheel hub, rear suspension and spring suspension for varying thickness to reduce the weight

of the entire wish bone suspension system. All these analysis are performed on complete

assembly of wishbone suspension as a future scope of work.


72

REFERENCE

1. Shigley’s Mechanical Engineering Design, 8Th

Edition.

2. Schaum’s outline of theory and problem of Strength of Materials / William A Nash

4Th

Edition.

3. S. Timoshenko Strength of Material, Elementary Theory and Problems 2nd

Edition.

4. Practicle Finite Element Analysis by Nithin S Gokulea, Sanjay S Deshpande, Sanjeev

V Bedekar, Anand N Thite, 1St

Edition.

5. Robert. D. Cook, Davis S MaIkus, Michael EPlesha: Concepts and applications of

Finite element Analysis, 3rd

Edition, John Wiley and Sons.

6. Ted Belytschko, Wing K Liu, Brian Moran: Non-linear Finite elements for Continua

and Structures, John Wiley and Sons.

7. W. C. Young, R. G. Budynas : Roark's Formulas for Stress and Strain, 7th

Edition,

McGraw Hill.

8. R.D.Cook, D.S. Malkus M. E. Plesha: Concept & applications of Finite Element

Analysis, 3rd

Edition John Wiley & Sons.

9. W. T. Thomson : Theory of Vibrations, 3rd

Edition, CBS Publishers & Distributors.

10. J. S. Rao, K.Gupta :The Theory & Practice of Mechanical Vibrations 5Th

Edition,

Wile Eastern Limited.

11. Kewal Pujara: Vibration & Noise For Engineers 4Th

Edition – Dhanpat Rai & Sons.

12. Erwin kreyszig : Advanced Engineering Mathematics, 5Th

Edition – Dhanpat Rai &

Sons.

13. V. Adams & A. Askenazi: Building Better Products with Finite Element Analysis,

Onward Press.

14. Introduction to Finite Elements in Engineering : Tirupathi R.Chandrupatla, Ashok D.

Belegundu, 3rd

Edition.

15. Introduction of Finite Element Analysis : S. Md. Jalaludeen, First Edition.

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